Specialised ship equipped with one or more large cranes (100–2 000 t SWL) for loading, transporting, and discharging oversized project cargo.
A heavy-lift vessel (HLV) is designed primarily for the carriage of outsized or extremely heavy project cargo that cannot be containerised or stowed in conventional cargo holds. The defining feature is one or more heavy-lift cranes with safe working loads (SWL) ranging from around 100 tonnes for smaller semi-submersible crane vessels to 2 000 tonnes for the largest dedicated lift vessels. Typical cargo includes oil and gas modules, refinery reactors, transformers, wind turbine components, yachts, locomotives, and military equipment.
Heavy-lift vessels are generally open-decked or have flush tweendeck configurations to accommodate irregular shapes. Tandem lift operations, where two cranes work in concert, can double the effective SWL. Prominent operators include BigLift Shipping, COSCO Heavy Lift, and Jumbo Maritime. Some vessels combine heavy-lift capability with semi-submersible ballasting for float-on/float-off (FLO/FLO) operations.
Regulatory oversight falls under SOLAS Chapter II-1 (structural and machinery requirements) and the ISM Code (SOLAS Chapter IX). Cargo securing plans must comply with the CSS Code (Code of Safe Practice for Cargo Stowage and Securing). Classification societies publish dedicated rules for crane design, pedestal foundations, and load-testing procedures. See the /reference/ship-types page for context alongside other project cargo vessel types.